The present invention relates to a member for supporting an EMC (electromagnetic compatibility) ferrite core.
Conventionally, for EMC use of devices, an EMC ferrite core has been widely used for preventing unintended electromagnetic radiation, which causes noises in electronic devices such as medical devices and OA appliances. In particular, cables that connect such electronic devices with external devices can be transmission channels of noise components. Thus, typically, at proximal end portions of the cables, which are connected to circuit boards, the EMC cores are used. The EMC cores are very important for preventing the noise components. However, they require dedicated securing structure, and the securing position inside the electronic devices is limited.
FIG. 5A is a perspective view showing an inner structure of an circuit unit 90, which is provided at a proximal end portion of a scope unit 50 of an electronic endoscope shown in FIG. 6. On a printed circuit board 89 inside the circuit unit 90, a CCD driving circuit for supplying driving signals to a CCD provided at the distal end of the scope unit 50, and a signal processing circuit that processes the output of the CCD are provided.
The external connector 81 is used for connection with a processor unit, which processes the output of the CCD and generates a video signal. Through cables 86c and 87c connected to connectors 86 and 87 on the printed circuit board 89, the processor unit is connected to the printed circuit board 89. The processor unit accommodates a light source, which emits light to a light incident portion 80. The light is directed through a light guide 75 to the tip end of the scope unit.
A cable 88c, which is connected to a connector 88 mounted on the printed circuit board 89, is a cable including a bundle of signal transmission wires connected to the CCD, which is provided at the distal end portion of the scope unit. In some cases, an insertion portion 51 (see FIG. 6) of the scope unit is several meters long, and the signal cable 88c also has the same length. In order to prevent unnecessary radiation of electro magnetic wave inside the circuit unit 90, the signal cable 88c is inserted through EMC cores 77 and 78. The EMC cores 77 and 78 are secured inside the circuit unit 90. For this purpose, as shown in FIG. 5B, which shows a cross section taken along line A-Axe2x80x2 of FIG. 5A, the EMC cores 77 and 78 are screwed on a side wall of a casing 100 using a supporting member 79. The circuit unit 90 is covered with a shielding cover 82 made of metal, which prevents unintended radiation of an electromagnetic wave from the printed circuit board 89.
As described above, an EMC core generally requires a particular supporting member, which is to be provided inside an electronic device. Further, a position where the supporting member is mounted inside the electronic device is limited. Therefore, using an EMC core may impede design freedom and/or sometimes prevent downsizing of electronic devices.
The present invention is advantageous in that an improved structure for securing an EMC core and a securing member used in such a structure are provided, which allows downsizing of devices, and provides improved design freedom.
According to embodiments of the present invention, there is provided an EMC core supporting structure for supporting one or more EMC cores inside a casing which accommodates a printed circuit board. The EMC core supporting structure includes a plate member capable of shielding electromagnetic waves. Preferably, the plate member expands inside the casing to substantially cover the printed circuit board, and at least one side portion of the plate member is connected to an inner wall of the casing. A supporting portion that receives the EMC core(s) is formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core on the plate member.
With this structure, since the plate member, which shields the electro-magnetic waves, is placed between the EMC core(s) and the printed circuit board, unintended or unnecessary electro-magnetic waves radiated from the printed circuit board will not reach the EMC core(s). Further, since the plate member functions for shielding the electromagnetic wave as well as for supporting the EMC core(s), it is not necessary to use an optional casing for shielding the printed circuit board.
In one embodiment, at least one side portion of the plate member includes a portion which is bent to form a U-shaped portion having two parallel surfaces facing each other and a connecting portion that connects the two parallel surfaces, the connecting portion being secured to the inner wall of the casing. Therefore, it is not necessary to provide a separate member for supporting the EMC core(s).
In a particular case, the at least one EMC core is held within a space defined by the two parallel surfaces and the connecting portion.
It is possible to secure the at least one EMC core and the connecting portion together on the inner wall using screws.
Alternatively, the at least one side portion of the plate member includes a portion that is bent to form an L-shaped portion, which is secured onto the inner wall of the casing.
In this case, an EMC core receiving portion may be integrally provided on the plate member, the at least one EMC core being held by the EMC core receiving portion. The EMC core receiving portion may be provided at any portion on the plate member. Thus, design freedom is well increased.
In a particular case, the EMC core receiving portion may have a U-shaped portion having two parallel surfaces and a connecting portion that connects the two parallel surfaces, the connecting portion being secured on the plate member, the at least one EMC core being held within a space defined by the two parallel surfaces and the connecting portion. Of course, any other configuration of the EMC core receiving portion can be employed.
Optionally, the L-shaped portion is secured on the inner wall using screws.
According to embodiments, only one side portion of the plate member is secured onto the inner wall, and an opposite side portion of the plate member may be bent to form a bent portion, which is bent toward the printed circuit board.
According to another aspect, there is provided a circuit board shielding structure employed in a casing which accommodates a printed circuit board, the shielding structure including a plate member capable of shielding electromagnetic waves, the plate member expanding inside the casing to substantially cover the printed circuit board, the casing having at least side walls capable of shielding electro-magnetic waves, each of the side walls being substantially perpendicular to the surface of the printed circuit board, the side walls surrounding the printed circuit board, at least one side portion of the plate member being connected to an inner surface of one of the side walls, a supporting portion that receives at least one EMC core being formed on a surface of the plate member opposite to a surface facing the printed circuit board for mounting the at least one EMC core on the plate member.
Optionally, the shielding structure may include a lower plate arranged on an opposite side of the plate member with respect to the printed circuit board, the lower plate being capable of shielding electromagnetic waves, the lower plate having an area covering the printed circuit board, the printed circuit board being shielded by the plate member, the side walls and the lower plate.
According to another aspect, there is provided an EMC core supporting member having a plate member capable of shielding electromagnetic waves, a supporting portion for supporting an EMC core is formed on one surface of the plate member, a connection portion is formed on a side portion of the plate member, the connection portion being formed by bending the plate member.
Further provided is an EMC core supporting member formed of a plate member capable of shielding electromagnetic waves, which includes a shielding portion, and an EMC core supporting portion which is formed by bending the plate member corresponding to an external shape of at least one EMC core so as to hold the at least one EMC core.
Optionally, the supporting member is provided inside a casing of an electronic device, the EMC core supporting portion having an area contacting the casing, the EMC core supporting portion being secured to the casing at the area contacting the casing with screws.
According to a further aspect, there is provided a shielding structure for shielding a printed circuit board employed in an electronic device, including an EMC core supporting member arranged on one side of the printed circuit board, a shielding plate arranged on the other side of the printed circuit board. The EMC core supporting member formed of a plate member is capable of shielding electro-magnetic waves, the EMC core supporting member having a shielding portion and an EMC core supporting portion which is formed by bending the plate member corresponding to an external shape of at least one EMC core so as to hold the at least one EMC core, the EMC core supporting portion being formed on a surface of the EMC core supporting member opposite to a surface facing the printed circuit board.
Optionally, a casing of the electronic device is made of metal, and the EMC core supporting member is electrically connected with the casing.